After his final conversation with Elend, Leras finally died, leaving Preservation without a Holder.[2][3] It would have quickly been absorbed by Vin, who was specially attuned to Preservation's power, except for the fact that she was still wearing her earring, which was Hemalurgically charged, acting as a repulsive factor.[4][5] The cognitive shadow of Kelsier was able to partially absorb the power of Preservation, helping to delay Ruin's destruction of the world, but could not wield its full power.[6]

During Vin's final battle with all of Ruin's Feruchemically enhancedSteel Inquisitors above Kredik Shaw in the abandoned Luthadel, Marsh tore out Vin's earring, with Kelsier using all of his strength to distract Ruin and help push Marsh's last vestige of willpower to rebel. Kelsier was already held under Preservation's Intent, and thus relinquished his hold on the power, becoming a Sliver, knowing Vin would still be able to override the Intent for a time.[6] Her body broken under the assault, Vin finally drew in the full power of Preservation, allowing her to nearly destroy all of the Inquisitors (save Marsh), and flatten Kredik Shaw, before fully Ascending.[7]

As Preservation, Ruin initially allowed her to flail about with her newfound power, knowing she would make mistakes. By clearing the air of ash, she allowed the too-near sun to bake the world in its deadly heat. Rotating the planet into night, to protect people from the sun's rays, she caused a massive tsunami, wiping out the coastline. As she reached to stop the tsunami, realizing she must be more subtle, Ruin stepped in to block her, taunting her failures. However, the two were at an impasse, as their power was evenly matched.[8] This was because a part of Ruin's "body", in the form of atium, had been hidden away by the Lord Ruler and the kandra in the secret Kandra homeland located adjacent to the Pits of Hathsin, kept secret in the Trustwarren. But the two were still able to influence those who wielded their investiture: Allomancy and Hemalurgy. This allowed Ruin to discover the secret cache by taking control of KanPaar following his coup of the First Generation and breaking of the First Contract and the Resolution. However, most of the kandra remained loyal when Ruin began to take hold and carried out the Resolution, removing their Blessings and sacrificing their sentience.[9][10][11]

Ruin sent his massive koloss army to attack the Pits, but Vin was able reach Elend, direct him to the Pits, and help him realize the truth behind the Mistfallen battalion: they were seers, mistings able to burn atium. Thus began the Battle of Hathsin, and Vin watched as Elend and most of his men died, holding off the koloss army, as they burned away the remaining atium in their sacrifice. With Elend dead, Vin had nothing left to live for and assaulted Ruin with all of her power, knowing it would kill both of them. She and Ati fell dead by Elend, outside the Pits, as Sazed watched, leaving both Ruin and Preservation unheld and the remaining, uncontrolled koloss to rampage among themselves.[12]

After Ati and Vin had perished, both Ruin and Preservation were unheld. Sazed, grieving over the bodies of Vin, who he assumed would be their savior, and Elend, noticed the black and white mists emanating from the bodies of the previous Vessels. With a sudden realization, he understood that he was the one who fit the prophecies of the Hero of Ages and absorbed the power of the two Shards. The two merged together under a single Vessel and became known as Harmony, and with their power Sazed set about fixing the world.[13][14]

The primary repercussion of the Final Ascension was the reforming of Scadrial. The two Shards, working in harmony together, were able to reform Scadrial back to a nearly identical world as it was like before the Lord Ruler's Ascension. Sazed had the ability to do this better than most, because of his duties as a Keeper and thus the knowledge stored in his metalminds, which he tapped as he drew in the power of Harmony. The religions he'd studied and rejected due to inconsistencies each held some truths about the past world, including cartography, geology, astronomy, anatomy, zoology, and artwork depicting the world's beauty.[13] The main exception was the region of Elendel Basin, which replaced the area where Hathsin once was and was designed to be a fertile cradle for civilization's renewal.[14]

In addition to correcting the position of the planet and reforming the landmasses, he returned the various lifeforms which had been lost and restored Humanity's physiology to how it had been, before they had needed to survive ashfalls and had been transformed by Rashek into altered skaa and nobility. He moved all of the survivors, who had moved underground for protection, to the new location of Elendel Basin, and left behind books chronicling the events of Mistborn Era 1 to be remembered by the population as well as a collection retaining the complete knowledge that had been collected by the Keepers.[13][15]

At Sliver Kelsier's behest, he endowed Spook with the abilities of a moderately powerful Mistborn. Unable to restore to life those that had passed on, he left the restored bodies of Vin and Elend for the survivors to honor. He also left Spook a cryptic message suggesting that there were two allomantic metals that were yet to be discovered.[15]

'Cata' is a common greek prefix which roughly translates to 'down' or 'reversal'. 'Cendre' is a French word for cinder or ash. Thus Catacendre can roughly translate both to an ashfall and/or the undoing of ash. Both meanings fit rather well for the events of the Catacendre, and it was later confirmed by Brandon to mean "the end of the ash".[16]